Investigation of cell behaviors on thermo-responsive PNIPAM microgel films.

The use of poly(N-isopropylacrylamide) (PNIPAM) as building blocks for engineering responsive coatings and their potential use as switchable substrates such as biosensors have attracted great attention in recent years. However, few studies have been conducted regarding the cell behaviors and the related mechanism on thermos-responsive surfaces consisting of PNIPAM microgel particles. In this work, monodisperse PNIPAM microgels were synthesized and used to prepare PINPAM microgel films. Uniform microgel surfaces can be fabricated by drop-coating with the precoating of a polyethylenimine (PEI) layer. Cell experiments indicate that unlike PNIPAM polymer brushes reported with controllable detachment ability, HepG2, which is a human liver carcinoma cell line, remains adherent on the microgel films upon cooling. Surface plasmon resonance (SPR) experiments show an irreversible adsorption of serum proteins on the microgel surface upon cooling, whose adsorption is a prerequisite of cell adhesion during cell culture. This fact may account for the irreversible adhesion of HepG2 cells.